Surface-charge-limited transient currents on insulating surfaces

Abstract

We have studied theoretically the flow of current across the surface of an insulator. We made the assumption that free injection occurred at one electrode, resulting in surface-charge-limited currents. We employed two geometries, the first corresponding to surface electrodes on one side of a thick dielectric, the second corresponding to a dielectric slab inside capacitor plates. In both cases, the current is proportional to the square of the applied voltage. The time-dependent currents approach the steady-state current from below with a time constant comparable to the surface transit time, but the detailed form of the current changes markedly with the geometry. Comparison with experiment suggests that the observed charge spreading does not occur by this surface-charge-limited mechanism.